Geothermal energy project stokes California town's earthquake fears

ANDERSON SPRINGS — Residents in this tiny Lake County community have complained for years about the earthquakes touched off by the geothermal energy projects that tap the vast reservoir of steam in the mountains behind their homes.

Now, with the federal government, Google and some of Silicon Valley's top venture capital firms committing millions to test a new way to mine clean energy from the earth here, the locals are finally getting some attention.

On a ridgetop above Anderson Springs, Bay Area startup AltaRock Energy Inc. is drilling a hole more than 2 miles deep. As soon as August, the company plans to inject high-pressure water to crack the solid, 500-degree Fahrenheit bedrock, creating an artificial reservoir of superheated water. The steam will then be used to drive electrical turbines.

If the test works, it could pave the way for essentially limitless exploitation of the heat energy in Earth's crust.

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Today, geothermal power is generated by tapping natural veins of steam, which are rare. Anderson Springs sits on the shoulder of the world's largest tapped geothermal site, one of only two major sites in the nation.

The technique AltaRock is piloting would make it possible to develop geothermal power anywhere there's hot, solid rock within a few miles of Earth's surface. Such sites are common, meaning that the new technology would open up a power source big enough, in theory, to meet the nation's entire energy demand thousands of times over – all without producing the greenhouse gases that contribute to global warming.

In Anderson Springs, though, the project has homeowners worried that the regular quake activity they already contend with would get even worse. Over the past two decades, the region has experienced between 13 and 32 earthquakes each year greater than magnitude 3.0 – including six in the past two weeks – according to U.S. Geological Service data, as well as thousands of smaller quakes.

While these are relatively small quakes, they originate near the surface and can feel stronger than the numbers suggest.